ABSTRACT Transporters catalyze entry and exit of molecules into and out of cells and organelles. They achieve cellular homeostasis, are responsible for multidrug resistance in pathogens and tumors, and, when defective, cause dozens of important human genetic diseases. Our laboratory maintains, updates and improves the Transporter Classification Database, TCDB, which houses the Transporter Classification (TC) system, adopted officially by the International Union of Biochemistry and Molecular Biology (IUBMB). TCDB is the internationally acclaimed, carefully annotated, universal standard for classifying and providing information about transporters and transport-related proteins in all major domains of life. It presents sequence, biochemical, physiological, pathological, structural and evolutionary data about these proteins and the transport systems they comprise. It uses a successful system of classification based on transporter class, subclass, family, subfamily, individual transport system and constituent proteins. It also includes a superfamily hyperlink. In this competitive renewal of GM0077402, we propose to continue to expand, update, and semi-automate TCDB. Our specific aims are to (1) upgrade TCDB by characterizing and categorizing protein domains and their topologies, motifs, repeat units, functional interactions, alternative splicing and post-translational modifications, (2) expand TCDB by implementing novel pipelines for data entry that will increase the coverage of transport diversity in TCDB while describing more effectively the complexity of multicomponent transport systems, (3) enter into TCDB transporter modulators such as activators, inhibitors, drugs and xenobiotics as well as internal and external conditions that influence transporter activities, while generating an ontology to describe the effects of chemical modulators that will complement our substrate ontology, (4) incorporate into TCDB synthetic pores/channels (TC subclass 1.D), and carriers (TC subclass 2.B), (5) introduce into TCDB connections between transport and metabolism and (6) expand our plans for long-term TCDB sustainability.